In recent years fiber optic light transmission systems, wherein a single optically-conductive fiber or multiplicity of parallel optically-conductive fibers are arranged to form a flexible light-conductive cable bundle for conveying light from one location to another, have come into increasing use, not only for providing illumination, but also for conveying data from one location to another. In the latter application, a light source is modulated with data to be transmitted at one end of the cable bundle, and the data is recovered at the other end of the cable bundle by a photo-sensitive detector. Since the data is conveyed by a medium not subject to radio frequency interference or detection, such light transmission systems are particularly well adapted for high security applications, such as found in the data processing and military communications field.
With the increasing use of fiber optic systems, the need has developed for a connector for optically coupling segments of light-conductive cables with minimum detriment to the optical transmission path. It is generally well known that to achieve efficient light transfer between a pair of fiber optic cables, the optical fibers of the cables must be axially and angularly aligned and spaced as close together as possible without touching. Where the fiber optic cables are used for conveying data, as the data transmission frequency is increased, the diameters of the fiber optic cables must be decreased to avoid dispersion and other deleterious effects within the optical transmission path. Data transmission frequencies have increased to the point where only a single optical fiber is utilized for conveying the data. As a result, the absolute magnitude alignment tolerance of the optical fiber ends is extremely small.
It has been found that extremely strict axial and angular alignment between a pair of fiber optic cables can be achieved by terminating the optical fibers of the cables in terminating pin assemblies with the optical fibers disposed along a preselected axis within the pins. As a result, when a pair of fiber optic cable terminating pins having optical fibers therein disposed along a preselected axis are aligned, the optical fiber terminating ends will also be in close alignment. It has been found that accurate alignment of optical fiber ends may best be achieved when the optical fibers are terminated within the terminal ends of the terminating pins concentrically aligned with respect to the outer dimensions of the terminating pin terminal ends. As a result, when a pair of such terminating pins are concentrically and accurately aligned, the optical fibers will likewise be accurately aligned for efficient light transfer. Such alignment is also independent of terminal pin rotation.
Many techniques have been devised for aligning optical fibers concentrically with respect to the outer dimensions of fiber optic cable terminating pins. One such technique which has proven successful is fully disclosed and claimed in copending application Ser. No. 806,953, filed June 15, 1977 in the name of the inventor of the present invention, and which is assigned to the assignee of the present invention. The connector pin assembly disclosed in that application includes a cylindrical terminating pin having a longitudinal bore extending into the rear end of the terminating pin and a counterbore extending into the terminating pin from the terminal end of the pin. The counterbore has inner walls which are concentric with respect to the outer dimension of the cylindrical terminating pin and communicates with the longitudinal bore. A plurality of pin members of equal diameter dimension are within the counterbore and arranged in side-by-side relation for substantial tangential contact with the inner walls of the counterbore and substantial tangential contact with each other. As a result, an optical fiber threaded through the longitudinal bore, the counterbore, and the central passageway defined by the pin members is concentrically aligned within the central passageway defined by the pin members with respect to the outer dimension of the terminating pin. For securing the optical fiber within the terminating pin, epoxy or other suitable adhesive material is introduced into the terminal end of the terminating pin to bond the optical fiber within the terminating pin at the terminating pin terminal end.
Another technique which has proven successful is fully disclosed and claimed in copending application Serial No. filed on Nov. 11, 1977, U.S. Ser. No. 849,055, also in the name of the inventor of the present invention, and which is also assigned to the assignee of the present invention. The technique there disclosed locates an optical fiber along a preselected axis within the terminal end bore of an fiber optic connector, such as the central axis of the connector, and is particularly adapted for high volume manufacturing production. A jig formed from cold flowable material and having a bore dimensioned for receiving the optical fiber is aligned by an indexing means so that the jig bore is aligned with the preselected axis. A force applying means, such as a collet chuck, exerts a uniform compressive pressure on the jig for causing the cold flowable material to flow about the optical fiber and locate the optical fiber along the preselected axis. Prior to exerting the uniform compressive pressure to the jig, epoxy or other suitable adhesive material is caused to flow into the terminal end bore of the fiber optic connector and around the optical fiber within the terminal end bore. As the collet chuck exerts the uniform compressive pressure to the jig, the epoxy is cured to securely bond the optical fiber within the fiber optic connector.
While the foregoing techniques have been found to be successful for locating an optical fiber along a preselected axis within the terminal end bore of a fiber optic connector, because adhesive material, such as epoxy is required for bonding the optical fiber within the fiber optic connector or terminating pins, these techniques are only suited for application in laboratory or manufacturing environments having the necessary equipment for preparing the adhesive material and curing the adhesive material. As a result, there is a need for a fiber optic cable connector pin assembly which may be utilized for accurately aligning and terminating an optical fiber in a field environment where specialized adhesive preparing and curing equipment is not available or which may be utilized by a user which does not have the specialized adhesive preparing and curing equipment.
It is therefore a general object of the present invention to provide a new and improved connector pin assembly which aligns and terminates an optical fiber of a fiber optic cable along a preselected axis of a fiber optic cable terminating pin.
It is a further object of the present invention to provide a new and improved connector pin assembly which concentrically aligns and terminates an optical fiber of a fiber optic cable with respect to the outer dimension of the connector pin which negates the heretofore required adhesive materials for bonding the optical fiber within the connector pin.
It is a still further object of the present invention to provide a connector pin assembly which is readily adapted for field termination of an optical fiber within the fiber optic connector pin.
It is a still further object of the present invention to provide a new and improved method for aligning and terminating an optical fiber of a fiber optic cable within a fiber optic cable terminating pin and which may be practiced in a field environment where specialized adhesive preparing and curing equipment is not available.